Life cycle assessment of Norwegian road tunnel

This paper estimates the life cycle environmental impacts of the standard road tunnel in Norway. The results can then serve as input to the environmental impact assessment in the planning of future road projects and as a tool to identify hot spots for reducing the environmental impacts from future tunnel projects.

This life cycle assessment (LCA) study follows the ISO 14040/44 methodology. The construction, operation and maintenance stages are assessed. The functional unit of this study is defined as ‘1-m standard Norwegian road tunnel with 100-year lifetime’. This study estimate the life cycle inventory by the following: (1) road tunnel construction tenders completed during 2004–2011 in Norway and (2) the Norwegian excavation practice of rock tunnels over the past 20 years. The Ecoinvent database provides the background data to the analysis.

The construction stage is found to contribute the most to the impact categories of climate change, photochemical oxidant formation, ozone depletion and terrestrial acidification. The consumption of concrete and explosives constitute the main elements causing these impacts. Equally, the construction stage is the main contributor to ozone depletion, caused by the consumption of bitumen and transport of materials. The maintenance stage contributes with 58 % of the particulate matter formation, due to the consumption of crushed aggregates and bitumen. The operation stage also plays a major role in human toxicity, ionising radiation and terrestrial ecotoxicity, contributing 57, 85 and 72 % of these impact categories, respectively, mainly due to the consumption of electricity. One Norwegian standard road tunnel emits at least 31 kt CO₂ eq greenhouse gases during its 100-year lifetime. The total greenhouse gases embodied in current the Norwegian road tunnel stock amount to at least 8.3 million tonnes, equal to 83 % of the total national direct CO₂ eq emissions due to road traffic in 2011. In recent years, around 150 kt CO₂ eq has been emitted annually to the atmosphere due to the construction, maintenance and operation of Norwegian road tunnels.

The policy implication from this study is that greenhouse gas emissions caused by the transport infrastructure is significant, and it is strongly recommended to be taken into account from the early planning phase of infrastructure projects in order to identify the best project proposal and to minimise the negative environmental impacts.